1. Field of the Invention
This invention relates to a granular composition for dentifrices, which is capable of giving an aesthetic effect to them and of being recognized its cleansing effect by the sensation of collapsing granules in the mouth. More particularly, this invention relates to a granular composition which will never give an unpleasant feel of foreign matter, though the granules incorporated in a dentifrice composition maintain such a strength that can be perceived as granules in the mouth, and will collapse slowly along the process of brushing the teeth. The invention also relates to a dentifrice composition comprising said granular composition.
2. Description of the Prior Art
It is known that dentifrice compositions are sometimes blended with granules or granule-like materials. The granules are generally prepared to contain functional substances such as medicaments, enzymes and polishers, or are incorporated in dentifrice compositions with a purpose of giving an aesthetic appreciation to the products. Some conventional dentifrice compositions contain a granular composition whose shape can be recognized in the mouth immediately after starting brushing but can no more be recognized along the brushing process, or cannot be recognized at all from the very beginning of the brushing. In the last case, the cleansing effect can only be confirmed with the eyes. Conventional binders of the granules are divided into two groups of water-soluble and water-insoluble substances. Examples of the water-soluble granular binders currently on use are certain polymer compounds including methyl cellulose and carboxymethyl cellulose. These water-soluble binders are good for granular compositions which are to be prepared into dry products of medicaments or the like. However, when they are incorporated in a composition containing much water such as dentifrices and facial cleansing cosmetics, the solidity of the granules significantly decreases and will collapse during the mixing process of manufacture or, even if collapsing is narrowly avoided, the granular shape can no more be maintained because of the humidity, and if ever maintained, the granular touch will never be sensed in the mouth, leading to unablement of recognizing cleansing effects contributed to the granules.
To solve the above problems, it has been proposed, among others, to use a variety of water-insoluble organic binders, which include a method disclosed in Japanese patent application Kokai Nos. 132249/1974 and 81594/1975 where wax blended with a pigment is made into a granular composition and a method disclosed in Japanese patent application Kokai No. 126906/83 where a powder of calcium carbonate or the like is prepared into granules by the use of a binder which is water-insoluble but soluble in ethanol. These granules, however, are still unsatisfactory in that when prepared to have such a solidity and size that will ensure the palpability of granules in the mouth, they give an unpleasant sensation of foreign matter though they are stable in the dentifrice composition. Moreover, concerning the aforementioned method of using wax, there is a difficulty in that ordinary granule formation methods of wet extrusion granulation method and spray-dry method are not appropriate in the practice. On the other hand, the method of using ethylcellulose dissolved in an organic solvent is accompanied by potential danger of fire, so that special fire-prevention devices and skilled operation are required.